Linux System User and Group Management Tutorial

This article provides a step‑by‑step guide to managing users and groups on a Linux system, beginning with an overview of login prompts and the distinction between the root ( # ) and regular user ( $ ) symbols.

It introduces basic user‑information commands such as id (showing UID and GID) and whoami (displaying the current username).

The adding users section describes the useradd command and its common options:

-d specify home directory

-M do not create a home directory

-u set UID

-g set GID

-s set login shell

Example of creating a default user:

useradd xiaoxu

The resulting entry in /etc/passwd looks like:

xiaoxu:x:1004:1004::/home/xiaoxu:/bin/bash

It also shows how to list available shells with cat /etc/shells and explains that /sbin/nologin disables login for a user.

Practice commands for adding users with specific options are provided, e.g.:

useradd xiaob -u 1009 -g 1004 -M -s /sbin/nologin

File‑viewing utilities such as head -5 /etc/passwd and tail -5 /etc/passwd are demonstrated.

The user switching section covers the su command, showing how to switch to another user ( su xiaoxu ), run a single command as another user ( su xiaoxu -c id ), and exit back to the original session ( exit ).

Deletion of users is performed with userdel . The article notes that userdel xiaoc removes the account but leaves the home directory, while userdel -r xiaod removes both the account and its home directory.

Modifying user attributes uses usermod :

-d change home directory

-g change primary group

-s change login shell

Examples:

usermod -d /opt/xiaoc xiaoc

usermod -g 1004 xiaoc

usermod -s /bin/bash xiaob

Password management is covered with the passwd command, which edits the /etc/shadow file. An example session shows changing the root password.

The permission management part explains user categories (administrator, regular user, system user) and the chown command for changing file ownership, including examples for changing user, group, or both.

Group management is introduced with groupadd to create groups, groupdel to delete them, and the /etc/group file as the configuration source.

Overall, the tutorial combines explanatory text with concrete command‑line examples to equip readers with the skills needed for effective Linux user and group administration.